Maybe you were thinking of tu-whit tu-whoo, which (variously spelt) is a conventional representation of the call of the tawny owl. It is used, for example, in this song from the end of Shakespeare's play Love's Labour's Lost: http://www.web-books.com/Classics/Poetry/Anthology/Shakespeare/WhenDaisies.htm In the song, the call of the owl, contrasted with the call of the cuckoo, seems to symbolize winter as a time of domestic cheer caused by absence of sexual distraction.